There are two types of leeches, those having three jaws and those having only a proboscis. The former, long worm-like animals, are free-swimming. When at rest they are found along the borders of bodies of water concealing themselves beneath stones or in the mud. The medicinal leech, Hirudo medicinalis, belongs to this group. Most of the latter are flat leaf-like creatures that live attached to the underside of stones, leaves, plants, or to their hosts. By means of suckers they move about after the fashion of "measuring worms."
Proceedings of the Iowa Academy of Science
©1925 Iowa Academy of Science, Inc.
"Some Observations on the Habits of Leeches,"
Proceedings of the Iowa Academy of Science, 32(1), 415-417.
Available at: https://scholarworks.uni.edu/pias/vol32/iss1/106